(POCOP)Ir-I(CO) [POCOP = kappa(3)-C6H3-2,6-(OPR2)(2) for R = Bu-t, Pr-i] and (PCP)Ir-I(CO) [PCP = kappa(3)-C6H3-2,6-(CH2PR2)(2) for R = Bu-t and Pr-i] complexes can add hydrogen via two distinct pathways. When R = Bu-t, (POCOP)Ir(CO) and (PCP)Ir(CO) complexes only add hydrogen via a proton-catalyzed pathway due to steric effects, yielding trans-dihydride complexes. For R = Pr-i, both systems oxidatively add hydrogen to give cis-dihydride complexes which thermally isomerize to more thermodynamically favorable trans-dihydride species, consistent with previous reports. Proton-catalyzed hydrogen addition pathways are also observed for both Pr-i-substituted (pincer)Ir(CO) complexes. (PCP)Ir(CO) complexes add hydrogen under milder conditions than the analogous POCOP species. Intermediate hydrido-pyridine Ir(III) carbonyl complexes from the proton-catalyzed pathway have been synthesized and characterized. This is the first report of a series of complexes shown to add hydrogen via concerted oxidative addition or a proton-catalyzed pathway to the same iridium center.
作者:Louise M. Guard、Travis J. Hebden、Donald E. Linn、D. Michael Heinekey
DOI:10.1021/acs.organomet.7b00434
日期:2017.8.28
A pair of POCOP-supported mono- and dicarbonyl complexes of Co have been prepared and crystallographically characterized. The reactivity of (tBuPOCOP)Co(CO) with H2, acids, and carbon monoxide has been compared to that of the previously reported Rh and Ir counterparts. Co is found to share reactivity traits with both Rh and Ir.